JPH10340019A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform rapid temperature rising by making a film moving speed from starting image formation till a recording material (paper) reaches a fixing unit lower than an image formation speed (paper feeding speed). SOLUTION: A fixing film 35 is started to be driven by a fixing and driving means M3 with the start of fixing temperature adjustment control. At this time, a control means controls the means M3 driving the fixing unit at PPS (pulse per second) which is lower speed than the paper feeding speed in the case of driving by a main body driving means in terms of step rotation. Since quantity of heat by a fixing heater 31 taken away by the film 35 and a pressure roller 36 is reduced in accordance with the lowering of the driving speed of the film 35 and the pressure roller 36, the quantity of heat at a fixing nip part N can be easily secured. Next, after the paper P is detected by a fixing entrance detecting means 38, the control means controls the means M3 at the PPS set to the paper feeding speed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art Conventionally, an unfixed image formed and supported on a recording material surface using a developer (toner) having a heat-fixing property by an appropriate image forming process means such as electrophotography, electrostatic recording, and magnetic recording. Various heat fixing devices have been proposed as devices for heat-fixing an image material image on a recording material surface.

[0003] For example, as an apparatus capable of achieving power saving and on demand, there is provided a heating element, a film which comes into contact with the heating element and moves together with a recording material, and a driving means for driving the film. A fixing device (hereinafter referred to as a "surf fixing device") for heating and fixing a visible image on a recording material via a film is used.

Since such a surf fixing device generally has a small heat capacity of a heating element or a film and can quickly raise the temperature to a predetermined fixing temperature, the surf fixing device is actually operated after the start of image formation (copy start) is instructed. It is possible to realize a waitless image forming apparatus in which the waiting time until the start of image formation is eliminated or extremely shortened.

[0005]

However, when the apparatus is used for the first time (hereinafter referred to as "Asaichi") for the first time under severe environmental conditions such as cold weather, the apparatus is cooled to the ambient temperature. And for a while,
Sometimes the characteristics of waitresses were impaired.

One of the factors that impairs the waitress is that the heat of the heating element is taken away by the movement of the cooled film or the pressure roller, and the temperature of the fixing nip does not reach the temperature regulation temperature.

At this time, the higher the moving speed of the film or the pressure roller, the more heat is deprived.
Since the conventional surf fixing device does not have its own means for determining the moving speed, the surf fixing device is configured to supply a driving force to the fixing device by a gear or a belt from a driving unit for conveying the paper of the main body. It is always driven at the same speed as the paper transport speed, and a constant amount of heat according to the paper transport speed has been continuously taken away.

Therefore, in the present invention, the amount of heat taken from the heating element between the start of image formation and the time when the recording material reaches the heating means is suppressed, and the image formation is quickly performed even when the apparatus is cooled. It is an object of the present invention to provide an image forming apparatus capable of performing the following.

[0009]

[Means for Solving the Problems]

[1]: Heat treatment by applying heat from a heating body to the recording material via a recording material conveying means, an image forming means for forming a visible image on the recording material, and a film moving with the recording material. In the image forming apparatus provided with a heating unit, the driving speed of the driving unit for driving the film is changed, and the film moving speed is changed from the start of image formation until the recording material reaches the heating unit. Control means for controlling the film moving speed to be the same as the recording material conveyance speed at the time of image formation after the recording material reaches the heating means, which is slower than the recording material conveyance speed at the time of image formation. Image forming apparatus.

[2]: Heat from a heating body is applied to the recording material via a recording material conveying means, an image forming means for forming a visible image on the recording material, and a film moving with the recording material. And a heating means for performing a heating process, the driving direction of the driving means for driving the film is changed, and the film is formed from the start of image formation until the recording material reaches the heating means. Is provided in a direction opposite to the direction in which the recording material is conveyed, and after the recording material reaches the heating unit, the film is moved in the same direction as the recording material in the direction in which the recording material is conveyed. An image forming apparatus characterized in that:

[3]: The control means changes the driving speed of the driving means, and changes the film moving speed from the start of image formation to the time when the recording material reaches the heating means at the time of image formation. The film moving speed is controlled to be the same as the recording material conveyance speed during image formation after the recording material reaches the heating means, which is lower than the recording material conveyance speed [2].
The image forming apparatus as described in the above.

[4]: Heat from a heating element is applied to the recording material via a conveying means for the recording material, an image forming means for forming a visible image on the recording material, and a film moving with the recording material. And a heating means for performing a heating process, the driving direction of the driving means for driving the film is changed, and from the start of image formation to the time when the recording material reaches the heating means. The film is moved in a direction opposite to the conveying direction of the recording material, and after the recording material reaches the heating means, the film is moved in the same direction as the conveying direction of the recording material, and the recording material is heated. An image forming apparatus comprising: a control unit that controls the film to move in a direction opposite to a conveying direction of the recording material after passing through the unit.

[5]: The control means changes the driving speed of the driving means, and changes the film moving speed from the start of image formation to the time when the recording material reaches the heating means at the time of image formation. After the recording material arrives at the heating means, the film moving speed is the same as the recording material conveyance speed at the time of image formation. The image forming apparatus according to [4], wherein the moving speed of the recording medium is controlled to be lower than the recording material conveying speed at the time of image formation.

<Action> In order to solve the above problems, the present invention provides:
With the above configuration, the amount of heat deprived of the film or the like by lowering the moving speed of the film from the start of image formation to the time when the recording material reaches the heating means, is lower than the image forming speed (paper conveying speed). An object of the present invention is to provide an image forming apparatus in which the temperature rise is suppressed and the temperature is quickly raised, and a waitress can be realized even under severe conditions as described above.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

<First embodiment> §1. FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

Reference numeral 1 denotes a document glass table on which a document is placed;
Is a pressure plate for holding a document. Reference numerals 3a to 3h denote an optical system including a document illumination lamp, a reflection mirror, an optical lens, and the like. M2 is an optical system driving means for driving these optical systems. In this embodiment, a stepping motor is provided.
It is composed of Further, the apparatus of this embodiment is of a document table fixed type, in which a document is scanned by scanner units 3a to 3d of the optical system to obtain a document image.

Reference numeral 4 denotes a photosensitive drum, which is driven to rotate clockwise as indicated by an arrow, and the drum surface is uniformly charged by a primary charger 5 in the course of the rotation, and is exposed to light L by the above-mentioned optical system. An electrostatic latent image corresponding to the image is formed.

Reference numeral 6 denotes a developing device for applying a developer (toner) on the drum surface to visualize a latent image on the drum surface. Reference numeral 14 denotes a developing device disposed below the photosensitive drum 4 for applying a transfer bias. A transfer means for transferring the toner image on the drum surface onto a recording material (paper), a cleaner 17 for removing toner and paper dust remaining on the drum surface after the transfer, and a cleaner 18 for removing the toner surface after the transfer by exposure. This is a full exposure lamp for removing residual voltage.
Reference numeral 19 denotes a transport belt that transports the paper P on which a toner image has been formed by these image forming means.

Reference numeral 20 denotes a fixing unit (heating means) for heating and pressing the paper P on which the toner image has been formed from the image forming means side to fix the toner image on the paper. Is controlled based on the temperature detected by the temperature detecting means 45.

7 is a paper feed cassette for loading and storing the paper P;
Reference numeral 15 denotes a manual paper feed unit, and reference numerals 8 and 16 denote paper feed rollers for feeding paper P in a paper feed cassette or a paper feed unit, respectively. The fed paper P is transported by transport rollers 11 and 12. The sheet is fed to the image forming means by the registration roller 13 at a predetermined timing.

M1 is a main body drive unit for driving each unit used for paper conveyance and image formation. Each unit used for forming a toner image around the photosensitive drum 4 as well as a paper feed roller 8, a conveyance unit b, and a discharge unit. A device for transporting the sheet P from the sheet feeding port to the sheet discharging port such as a roller 21 is driven. The main body driving means M1 of this embodiment is constituted by a DC servo motor. M3 is a fixing driving unit that drives a film or the like of the fixing unit 20.

§2. FIG. 2 is a block diagram of a control system in the image forming apparatus.

In this embodiment, the control means 100 is constituted by using an electronic element represented by a microcomputer or the like.

The control means 100 controls the apparatus itself and controls image formation in accordance with the operation of the operation means 101 and signals from the sensors. Further, the fixing heater driving means 102 supplies a current to the fixing heater 31 so that the fixing heater 31 is energized.
This is a means for generating heat in the heater 31, and usually uses a transistor or a triac, which is an electric element. In the present embodiment, an AC power supply is used as a power supply to the device,
The fixing heater driving means 102 controls the energization of the fixing heater 31 by phase control.

The fixing driving means M3 is also electrically connected to the control means 100 like the other means.

In the figure, the solid arrows indicate that they are electrically connected, the broken arrows indicate that heat is acting, and the direction of the arrows indicates the direction of action.

When the copy mode and the number of copies are set by the operation means 101 provided in the main body of the image forming apparatus, and the start key is pressed, the control means 100 controls the mode selected by the operation means 101. Starts image formation in accordance with
A description will be given of a case where the 1: 1 copy mode is selected.

When the control means 100 detects that the start key has been pressed, the control means 100 controls the power supply to the fixing heater 31 based on the temperature detected by the temperature detecting means 45 using the fixing heater driving means 102. , The temperature of the fixing unit 20 is controlled.
Further, the illumination lamp 3a is turned on, the positions of the scanner units 3a to 3d of the optical system are moved to the home position using the optical driving means M2, and the position of the optical lens is changed to a known means such as an optical lens. Then, it is adjusted to the same-magnification position by using the driving means (not shown), and is prepared (initial of the optical system). Alternatively, if the position is the same size, the next operation is performed.

At the same time, the main body driving means M1 is driven to control the paper conveyance and image forming process to proceed at a predetermined speed.
Prepare to perform an image forming operation.

Next, the paper feed roller 8 is driven so that the paper P is fed and transported on the paper transport path. Then, the sheet P is separated and fed one by one from the cassette 7 and fed by the driving rollers 11 and 12 to obtain the registration roller 13.
Reach up to.

After the preparation of the optical system is completed, the optical system starts reading, and matches the image leading edge detection signal with the on-time of the registration roller 13 to form a toner on the photosensitive drum 4. The control is performed so that the image and the leading edge of the sheet P are aligned and, at the same time, reach the transfer position below the drum.

Further, by applying a transfer bias from the back side of the sheet P which has reached the transfer position at the transfer section 14, the toner image is transferred to the sheet P, and the sheet P is fixed by the transport belt 19 to the fixing unit. 20 and the fixing unit 20
Then, the paper P carrying the toner image is subjected to a fixing process by applying pressure and heat to the paper P, and the paper P is discharged onto a discharge tray 22 outside the apparatus by a discharge roller 21.

§3 Fixing Unit (Heating Means) The fixing unit 20 of this embodiment is called a surf fixing device using a ceramic heater, and will be described in detail below. FIG. 3 is a schematic configuration diagram of the fixing unit 20.

In the figure, reference numeral 31 denotes a ceramic heater.
And a heater section 35 composed of a thermistor, etc., is an endless fixing film, and the fixing film 35 is suspended between the heater section 31 and the tension rollers 33, 34. ing. Reference numeral 36 denotes a pressure roller, which presses against the heater section 31 with the film 35 interposed therebetween to form a nip portion N. The pressure roller 36 is rotationally driven by the fixing driving means M3, so that the film 35 is rotationally moved, and the winding roller 34 and the tension roller 34 are rotated.
Is driven by the rotation of the film 35. Although the fixing driving means M3 of this embodiment is constituted by a stepping motor, it is apparent that the same effect can be obtained by using any motor capable of controlling the speed. is there. In addition, the transmission means is not limited to the motor, and may be a transmission means for transmitting the driving force from the main body driving means M1 to the pressure roller 36 by reducing the driving force.

The heater section 31 includes a so-called ceramic heater in which a resistance heating element 42 is provided on a ceramic substrate 41 and the resistance heating element 42 is covered with a glass protective layer 44, and a temperature provided on the back surface of the substrate of the ceramic heater. Detecting means 45,
It comprises a support member 32 for supporting the ceramic heater.

The temperature detecting means 45 detects the temperature of the nip N, arranges an element usually called a thermistor on the substrate surface, measures a voltage value divided by an electric resistance or the like, and measures the temperature. Is a known means for detecting

Reference numeral 38 denotes a flag portion (light shielding plate) which is swingably provided with one end protruding into the paper transport path.
This is a fixing entrance paper detecting means composed of a pair of a photo interrupter 38b and a gap type photo interrupter 38b. When the paper P is conveyed, the light shielding plate 37 is pushed down and enters the gap of the photo sensor 38b, The light beam between the light emitting and receiving portions of the interrupter 38b is blocked. And the paper P
Passes, the flag portion 38a returns to the upper side, retreats from the gap, and the light beam from the light projecting portion of the photo interrupter 38b enters the light receiving portion. It is output as a signal. Similarly, reference numeral 39 denotes a fixing exit paper detecting means constituted by a pair of a flag section 39a and a photo sensor 39b.

The fixing entrance paper detecting means 38 is a fixing unit 2
The sheet P is provided near the entrance of the sheet P, and by detecting the leading end of the sheet P, it can be detected that the sheet P enters the fixing unit 20.

Similarly, the fixing outlet paper detecting means 39 is provided near the outlet of the fixing unit 20 and detects the trailing end of the fixed paper P, thereby fixing the paper P from the fixing unit 20 and discharging it. Can be detected.

The signals from the fixing entrance paper detecting means 38 and the fixing exit paper detecting means 39 are inputted to the control means 100 (not shown in FIGS. 1 and 3), and are sequentially monitored. .

§4. Temperature Control / Drive Control Next, control of the fixing unit 20 will be described. FIG. 4 shows the general flow of this control.

After the power is turned on, the control means 100 waits until the copy start key is pressed, and when the copy start key is detected, the next step is performed (S1). Upon detecting that the copy start key has been pressed, the main body driving means M1 and the optical system driving means M
2 to initialize the optical system and
Feed. In addition, the fixing temperature control is started, and accordingly, the driving of the fixing film 35 by the fixing driving unit M3 is also started. At this time, in the present embodiment, the control unit 100 controls the fixing driving unit M3 for driving the fixing unit 20 so that the PPS having a lower speed than the paper conveyance speed driven by the main body driving unit M1.
(Pulse Per Second) to control step rotation. (S
2) Then, the fixing heater 31 causes the film 35 and the pressure roller 36 to be driven by the slower driving speed.
5 and the amount of heat taken by the pressure roller 36 is reduced.
The amount of heat in the fixing nip portion N shown in FIG. 3 is easily secured, and the amount of heat is sufficiently secured from the time when the above-described paper P is fed to the time when the sheet P reaches the fixing unit 20. You.

Whether or not the preparation of the optical system is completed (S
3) Whether the paper P has been properly transported (S4)
Is detected, and if the preparation of the optical system and the conveyance of the sheet have been properly performed (OK), the image formation is started. (S5) After the sheet P is detected by the fixing entrance detecting means 38,
The control means 100 controls the fixing driving means M3 with PPS according to the paper transport speed. As a result, the paper conveyance speed of the fixing unit 20 and the paper conveyance speed of the apparatus main body become the same as the image forming speed, so that the paper P is conveyed inside the fixing unit without delay and the fixing process is performed properly. .
At this time, since the temperature of the fixing nip N is sufficiently raised, it is possible to perform the fixing control to obtain sufficient fixing property for the sheet P.

As described above, according to the present embodiment, the temperature of the fixing nip N is hardly deprived, and the fixing temperature can be easily reached. For this reason, the fixing temperature is quickly reached even at the start-up in the morning in cold weather, so that it is possible to realize a waitress without the waiting time for the fixing control.

<Embodiment 2> In this embodiment, the fixing unit 20 is reversely rotated from the start of image formation until the paper reaches the heating means. Is not different from the first embodiment. Therefore, changes in the fixing control will be described below. FIG. 5 shows a general flow of this control.

When the fixing driving means M3 is rotated in the direction of arrow A, the fixing unit 20 (film 35) is rotated.
The driving direction of the fixing unit 20 is configured to be driven in a direction opposite to the sheet conveying direction when the fixing unit 20 rotates in the direction opposite to the arrow A direction.

In this embodiment, when it is detected that the copy start key has been pressed, the control means 100 controls the fixing driving means M3 for driving the fixing unit 20 with the low-speed PPS and in the direction opposite to the paper transport direction (shown in FIG. 1). (Step S2 ').

Then, the paper P is detected by the fixing entrance paper detecting means 38.
After detecting the state where the leading edge of the paper enters the fixing unit 20, the fixing driving unit M3 is stopped from the reverse rotation of the arrow A,
Further, the control means 100 controls to rotate in the direction of arrow A (positive direction) at the paper transport speed (S7 ').

In this way, when the paper P is introduced into the fixing unit 20, the portion heated during the reverse rotation of the film 35 and the pressure roller 36 comes into contact with the paper P. , And more stable fixing property can be realized.

<Embodiment 3> FIG. 6 shows a general flow of control in Embodiment 3.

In this embodiment, after forming an image in the same manner as in Embodiment 2, the paper P passes through the fixing unit 20 and
The trailing edge of the sheet P is detected by the fixing exit sheet detecting means 39 (S7).
After 1), control is again performed so that the fixing driving unit is slowly driven in the direction opposite to the arrow A direction. (S72) Accordingly, the control unit 100 determines that the paper P is
When the sheet P is at 0, the sheet P is rotated in the direction of arrow A to perform the fixing process. When the sheet P is not present in the fixing unit 20, the sheet P is driven to rotate slowly in the direction opposite to the arrow A. .

<Others> The driving method of the film is not limited to the above-described embodiment, but may be the following. FIG. 7 (a), (b), (c)
1 is a schematic configuration diagram showing another type of apparatus.

The device (a) has a heater 3 as a heating element.
An endless belt-shaped fixing film 35 is suspended and stretched between three members 1, a driving roller 33 ′, and a tension roller 34, and the driving roller 33 ′ is driven by fixing driving means M 3 to rotate the fixing film 35. It is like that. The pressure roller 36 is driven by the rotation of the fixing film 35.

The device (b) has a heater 3 as a heating element.
1 and a support member 32 supporting the heater 31 on the lower surface side.
A fixing film 35 having a cylindrical shape loosely fitted to the outside of the support member 32; and a pressure roller 36 pressing the heater 31 with the film 35 therebetween to form a fixing nip portion N. This is a so-called tensionless type device in which the pressure roller 36 is driven by the driving means M3 to rotate the fixing film 35.

The device (c) uses a rolled long end film as the fixing film 35, which is fed from a feeding shaft 47 via the heater 31 to a winding shaft 4.
8 so as to travel at a predetermined speed.

In the apparatus having such a configuration, the same effects as those of the above embodiment can be obtained by controlling the fixing driving means M3 and the like according to the present invention.

[0057] The heating element (heater) is not limited to the ceramic heater of the above embodiment, but may be another heating method.
For example, an electromagnetic heating method in which an induced current is generated by applying a magnetic force to a conductive and ferromagnetic member such as iron, copper, cobalt, nickel, and chromium to generate heat, and the member is also applicable. At this time, the member is formed in a plate shape,
Instead of 1, it may be configured to be supported by the support member 32, or may be configured to include the member as a metal layer of the fixing film 35.

[0058]

As described above, according to the present invention,
An image forming apparatus capable of suppressing the amount of heat taken from the heating element between the time when the image forming is started and the time when the recording material reaches the heating unit and capable of quickly forming an image even when the apparatus is cooled. The purpose is to provide.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus of the present invention.

FIG. 2 is a block diagram of a control system according to the first embodiment.

FIG. 3 is a schematic configuration diagram of a fixing unit according to the first embodiment.

FIG. 4 is a flowchart of control according to the first embodiment.

FIG. 5 is a flowchart of control according to a second embodiment.

FIG. 6 is a flowchart of control according to a third embodiment.

FIG. 7 is an explanatory diagram of another configuration of the fixing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original platen glass 2 Pressure plate 3a Original illumination lamp 3b 1st mirror 3c 2nd mirror 3d 3rd mirror 3e Optical lens 3f 4th mirror 3g 5th mirror 3h 6th mirror M2 Optical drive means 7 Paper feed Cassette 8 Paper feed roller 11, 12 Transport roller 13 Registration roller 19 Transport belt 21 Discharge roller M1 Main body driving means 4 Photosensitive drum 6 Developing device 14 Transfer charger 20 Fixing unit M3 Fixing drive Means 31 Heater 32 Supporting member 33, 34 Tension roller 35 Fixing film 36 Pressure roller 100 Control means 101 Operating means 38 Fixing inlet paper detecting means 39 Fixing outlet paper detecting means

Claims (5)

[Claims] 1. A recording material conveying means, an image forming means for forming a visible image on the recording material, and a heat applied to the recording material by applying heat from a heating body to the recording material via a film moving with the recording material. An image forming apparatus having a heating means for processing, wherein the driving speed of the driving means for driving the film is changed,
From the start of image formation to the time when the recording material reaches the heating means, the film moving speed is slower than the recording material conveyance speed at the time of image formation. An image forming apparatus comprising: a control unit that controls a moving speed to be equal to a recording material conveying speed during image formation. 2. A recording medium conveying means, an image forming means for forming a visible image on the recording material, and a heating element for applying heat from a heating body to the recording material via a film moving with the recording material. An image forming apparatus having a heating unit for performing processing, wherein a driving direction of a driving unit for driving the film is changed,
The film is moved in a direction opposite to the conveying direction of the recording material after the image formation is started and before the recording material reaches the heating unit, and the film is moved after the recording material reaches the heating unit. An image forming apparatus comprising: a control unit that controls the recording medium to move in the same direction as the recording material conveyance direction. 3. The method according to claim 1, wherein the control unit changes the driving speed of the driving unit, and changes the film moving speed from the start of image formation until the recording material reaches the heating unit. 3. The image forming apparatus according to claim 2, wherein, after the recording material reaches the heating unit, the film moving speed is controlled to be equal to the recording material conveyance speed during image formation. 4. A recording material conveying means, an image forming means for forming a visible image on the recording material, and applying heat from a heating body to the recording material via a film moving with the recording material to heat the recording material. An image forming apparatus having a heating unit for performing processing, wherein a driving direction of a driving unit for driving the film is changed,
From the start of image formation until the recording material reaches the heating unit, the film is moved in a direction opposite to the conveying direction of the recording material, and after the recording material reaches the heating unit, Control means for moving the film in the same direction as the conveying direction of the recording material, and for controlling the film to move in a direction opposite to the conveying direction of the recording material after the recording material has passed the heating means; An image forming apparatus comprising: 5. The method according to claim 1, wherein the control unit changes a driving speed of the driving unit, and changes a film moving speed during a period from the start of image formation to a time when the recording material reaches the heating unit. Slower than the speed, the film movement speed after the recording material reaches the heating means is the same as the recording material conveyance speed during image formation, and the film movement speed after the recording material passes through the heating means. 5. The image forming apparatus according to claim 4, wherein the control is performed at a speed lower than a recording material conveyance speed during image formation.